Two degrees of freedom optical table

ABSTRACT

The design of a high precision optical table with two degrees of freedom. The table will be for use with surface optical table applications as well as other engineering experiments. It will provide a surface with rock solid stability and rigidity to support demanding research applications. The flatness of the table is an outstanding &lt;±0.004 inch flatness over two square feet, and is combined with several frequency damping measures both in the work surface and the base of the optical table. Experimental apparatus&#39; mounted on the work surface can be positioned and oriented anywhere in three-dimensional space within the limits of travel via high precision X- and Z-axis motion stages, specifically four jacks, two slides and two free slides.

CROSS REFERENCE TO RELATED APPLICATIONS

Not applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

SEQUENCE LISTING OR PROGRAM

Not Applicable

BACKGROUND OF THE INVENTION

The invention described herein is related to the field of optics experiments and engineering. In these applications, especially optic experiments, the alignment of each individual component must be extremely accurate. Optical tables serve as moveable mounting surface for precision optical instruments, providing an extremely flat work surface for such instruments. The table is constructed of high quality materials which prevent to resonating transmission of vibrations, provide extreme rigid stability for the attached instruments, and have high accuracy in repeatability for said experiments and engineering applications.

SUMMARY OF THE INVENTION

The device provides high precision X- and Z-axis motion using high load capacity positioning stages. The work surface can be precisely moved vertically and horizontally. Experimental apparatus' mounted on the work surface can therefore be positioned and oriented anywhere these dimensions within the limits of travel. These movements are accomplished by the combination of vertical linear actuators, utility jacks, and linear slides. These actuators combined comprise the manipulation system for the optical table. Each actuator is equipped with linear encoders.

BRIEF DESCRIPTION OF DRAWINGS

The invention as described herein with references to subsequent drawings, contains similar reference characters intended to designate like elements throughout the depictions and several views of the depictions. It is understood that in some cases, various aspects and views of the invention may be exaggerated or blown up (enlarged) in order to facilitate a common understanding of the invention and its associated parts.

FIG. 1 is a schematic of the overall optical table.

FIG. 2 is a schematic of the optical table with breadboard removed.

FIG. 3 is a schematic of one of the jacks.

FIG. 4 is a schematic of one of the slides.

FIG. 5 is a schematic of the kinematic foot.

FIG. 6 is a schematic of the bubble level.

DETAILED DESCRIPTION OF INVENTION

Provided herein is a detailed description of one embodiment of the invention. It is to be understood, however, that the present invention may be embodied with various dimensions. Therefore, specific details enclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or manner.

As seen in FIG. 1, the two degrees of freedom optical table is a high precision motorized optical table employing an arrangement of standard products to create a table with two degree of freedom positioning capabilities. The table is for use in precision optical experiments and several other engineering applications. The surface of the table is where the precision equipment is mounted. This surface, better known as a breadboard 7, provides a flat and rigid surface to which said experimental apparatus' and other equipment can be mounted on the grid of M6 style holes.

The breadboard used in this embodiment is the highest grade, research grade, from Newport Corporation to provide rock-solid stability and rigidity to support demanding research applications. When installed in this optical table application, it is mounted to four breadboard mounting surfaces 8, seen in FIG. 2. It is available in two and four inch thicknesses and demonstrates an outstanding <±0.004 inch flatness over two square feet. The working surface features a ferromagnetic stainless steel surface with cut threads with countersink type mounting holes and has an integrated high frequency damping layer, two types, as well as self-damping side panels. The damping layer prevents a resonant response from being transferred throughout the table for vibrations produced on the table lower than the frequency of the damping layer. The core design of the breadboard is a trussed honeycomb style, with vertically bonded closed cell construction, steel sheet materials and triple core interface. The breadboard also features an easy clean conical cup constructed of a non-corrosive high impact polymer material [1].

The system base frame 9 is comprised of welded tubular steel with a powder coated finish. To work in conjunction with the damping layers in the breadboard, the frame base is filled with sand to provide extra damping effects. The table comes with three casters the facilitate movement and positioning of the table. The frame is supported on four feet 10 when the table is in use. The feet are attached to the four table legs 11. As seen in FIG. 5, these feet have eight adjustment screws 12 to align table height and transverse position with an accuracy of 0.25 mm as well as floor mounting holes 13 to anchor the table to the floor and adjust and lock the parallelism of the table with respect to the floor (pitch and roll) within ±50 μrad. The frame is also fitted with adjustable shoes 14 and bubble levels 15 for adjusting roll, pitch and yaw, x, y and z position, as seen in FIG. 6.

The table provides high precision X- and Z-axis motion using high capacity positioning stages. The work surface can be precisely moved vertically and horizontally. The experimental apparatus' that will be mounted to the work surface can therefore be positioned and oriented anywhere these dimensions within the limits of travel. These movements are accomplished by an arrangement of two arrangements of stepper-motor-actuated jacks and slides, two free slides, and two separate jacks attached via spherical bearings 8, seen in FIG. 2. All four jacks 16 are controlled as one, using a vertical motion stepper motor 26. The two actuated slides 17 are driven as one, pushing the two free slides 18 using a horizontal motion stepper motor 27. With the breadboard 7 attached, to the actuated slides and the subsequent free slides, the actuation horizontal motion allows the free slides 18 to slide horizontally in sync with the actuated slides 17 without stepper motors.

The stepper-motor-actuated jacks 16 used in this embodiment are four precision crossed roller jacks, seen in FIG. 3. These high precision jacks provide an accurate and rigid platform for the overall positioning system. The rugged black anodized aluminum housing 19 features a precision ground base and top plate 20, each with multiple utility holes 21 which are used to attach each precision jack to the breadboard mounting spherical bearings 8, subsequently attached the breadboard work surface 7. The vertical stages for each jack are driven by a single, high class preloaded ball screw coupled to a high torque 200 step per revolution stepper motor which can be run in full, half, or microstepping mode to meet whichever specification is required of the overall positioning system. Maximum rigidity is assured through the use if preloaded crossed roller linear bearings, featuring two adjustable, normally closed limit switches at the end of travel.

The stepper-motor-actuated slides 17 used in this embodiment are two precision crossed roller slides, seen in FIG. 5. These high precision linear slides provide an accurate and rigid platform for the overall positioning system. The rugged black anodized aluminum housing 22 features a precision ground base and top plate 23, each with multiple utility holes 24 which are used to attach each precision slide to the breadboard mounting spherical bearings 8, subsequently attached to the breadboard work surface 7. The stages for the two actuated slides are driven by a single, high class preloaded ball screw 25 coupled to high torque 200 step per revolution stepper motor which can be run in full, half, or microstepping mode to meet whichever specification is required of the overall positioning system. Maximum rigidity is assured through the use of preloaded crossed roller linear bearings, featuring two adjustable, normally closed limit switches at the end of travel. With the breadboard attached to the system, the actuator controlled slides subsequently push the free slides 18 in the horizontal direction of travel.

The stepper motor controllers used for both the high precision jacks and high precision slides are high-performance, integrated motion controllers and drivers offering outstanding trajectory accuracy and exceptional programming functionality. The controller and driver combines simplicity of operation with advanced features to precisely control the most diverse displacement and synchronize them via measurement, command, or external acquisition strings. Supplying 500 Watts of motor driver power, the stepper motor controller and driver can handle up to four axes of motion using any combination of slides and jacks, although in this application, only two axes are required.

This table facilitates to use of linear encoders, sensors which encode a position, which can be decoded into a position by a motion controller. The linear encoders used in this application are Numerik Jena LIK21 series encoders, considered to be in the compact model range. These encoders have extremely small dimensions of scanning head for crowded installation conditions, high insensitivity to contamination of scale tapes due to two optical sensors in the scanning head, as well as high resolution and accuracy [2]. The use of encoders ensures accuracy and repeatability of jacks and slides positioning to a resolution of 0.1 microns.

The overall table has a load capacity of 454 kilograms (approximately 1000 pounds) when the load is centered. The travel limits of the slides and jacks are set to specification based upon the movement required of the optical equipment attached to the breadboard work surface and experimental requirements, but change with table position in the X- and Z-direction. The pitch (rotation in the vertical plane) has a resolution of 0.1 μrad range +/−100 μrad. The roll (rotation in the horizontal plane) has a resolution of 0.1 μrad range +/−100 μrad. The yaw (rotation around the vertical axis) has a resolution of 0.1 μrad range +/−100 μrad. Vertical travel maximum is ten inches. Horizontal travel maximum is two inches. The slides horizontal actuator full step resolution is 5 microns. The jacks horizontal actuator full step resolution is 1.25 microns. 

What is claimed is:
 1. An optical table with two degrees of freedom, comprising: (a) A breadboard work surface; (b) Two high precision slides; (c) Two free slides; (d) Four high precision jacks; (e) Two stepper motor/drivers; (f) Six linear encoders; (g) Base frame; (h) Four feet.
 2. The apparatus of claim 1 wherein said optical table has two degrees of freedom due to the stages being arranged in two groups of actuated slides and jacks, with two free slides.
 3. The apparatus of claim 1 wherein said breadboard work surface is mounted on four mounting surfaces via four spherical bearings.
 4. The apparatus of claim 3 wherein said breadboard work surface is where optical equipment is attached via a grid of M6 style holes.
 5. The apparatus of claim 3 wherein said breadboard is a research grade breadboard from Newport Corporation.
 6. The apparatus of claim 3 wherein said breadboard features a ferromagnetic stainless steel with two types of integrated high frequency damping layers as well as self-damping side panels.
 7. The apparatus of claim 3 wherein said breadboard is moved in the horizontal direction via high precision slides of claim
 1. 8. The apparatus of claim 1 wherein said slides have rugged black anodized aluminum housing.
 9. The apparatus of claim 8 wherein said high precision slides are driven collectively by a high class preloaded ball screw coupled with preloaded crossed roller linear bearings, and push said free slides of claim 1 when actuating.
 10. The apparatus of claim 8 wherein each said slide features two adjustable limit switches at the end of travel.
 11. The apparatus of claim 3 wherein said breadboard is moved in the vertical direction via high precision jacks of claim
 1. 12. The apparatus of claim 1 wherein said jacks have a rugged black anodized aluminum housing,
 13. The apparatus of claim 12 wherein said jacks are driven as one by a high class preloaded ball screw coupled with preloaded crossed roller linear bearings.
 14. The apparatus of claim 12 wherein each said jack features two adjustable limit switches at the end of travel.
 15. The apparatus of claim 1 wherein said slides and jacks are controlled using high performance, integrated motion controller/drivers, supplying 500 Watts of power to each individual slide and jack.
 16. The apparatus of claim 1 wherein said linear encoders are Numerik Jena encoders that ensures accuracy and repeatability of both jacks and slides positioning.
 17. The apparatus of claim 1 wherein said base frame is comprised of welded tubular steel with a powder coated finish.
 18. The apparatus of claim 17 wherein said base frame is filled with sand.
 19. The apparatus of claim 1 wherein said feet are attached to the four legs of the overall table.
 20. The apparatus of claim 19 wherein said legs have adjustment screws to align table height and transverse position as well as floor mounting holes to anchor the table to the floor and adjust and lock the parallelism of the table with respect to the floor (mounting surface). 